By Frances Saunders

Whether it’s a formal or informal garden style, the plant selection process is the same. Establish some criteria, consider plant placement based on a plant’s mature size, and you won’t get it wrong.

 Careful plant selection and placement goes a long way to ensuring your garden is sustainable – a garden where the plants thrive and, hopefully, only die of old age.

Careful plant selection starts with a site analysis. What sort of soil do you have? That is, is it clay or sandy and what is its pH? What direction does the garden face? When does any area receive shade from things like trees and buildings? What rainfall do you have, or can you provide irrigation from a sustainable source such as a water tank? What sort of climate, such as tropical or temperate? Do you have frosts and how severe? And are there any microclimate considerations, such as that damp corner on the south side that receives no sun? Is it windy? Is it coastal?  Are there any existing plants that need to be considered, such as mature trees? What about slope?

There’s more! Regardless of the style of the garden preferred (that is, formal or informal), I’m sure readers are keen on creating a garden rich in bio-diversity, to attract birds and other useful and delightful critters that will ensure minimal pest and disease problems?   Then you need to consider plants that contribute the best in this function.

There are also needs and wants. Perhaps you need a climber for somewhere, or a plant that can be hedged to two metres, or you particularly like fragrant flowers. Obviously plants you select also have to be visually appealing to you too.

How you answer these questions forms the basis for your plant selection criteria and means you can select plants that will grow and thrive in the various areas of the garden. There will be fewer plant deaths and no mistakes, thus making it more sustainable.  For example, imagine in ten years’ time that beautiful tree you selected and planted has to be removed because its mature size hadn’t been considered and now it’s getting too big for the space. Or perhaps the plants didn’t suit the site conditions and one by one they all died.

That brings me to plant placement. If you are starting from scratch, drawing up a plan of your garden based on accurate measurements will help you think about what you want to do with the space, eg you want a two metre hedge along the front.

Regardless of whether you are starting a new garden or replacing plants in an existing garden, a most important aspect of selection and placement is knowing what size the plant will be at maturity.

If you are drawing up a plan, plants are shown at their mature spread/width/canopy. This means you will not over or under plant the space, and will also avoid unfortunate mistakes like not allowing them enough space.  In the case of a hedge, this is shown on the drawing whatever width you will maintain it at once you have decided on the plants that fulfil the size criteria but remember not to plant a hedge right on the boundary – set it back enough to allow that width to establish.

There is much more to consider if we want our plants to only die of old age, such as plant maintenance requirements and maintaining soil health, but these are for other articles.


Someone didn’t think about the mature size of this Phormium and it was planted too close to the path, so it has to be hacked back like this all the time. In time a decision will undoubtedly be made that an entire border of them needs to be removed.


Photographs: Frances Saunders

Footnote:  Simon Branson, Director of Green Change Solutions, and Frances Saunders, landscape & horticulture teacher at Chisholm Institute TAFE and former SGA employee, are teaming up to develop a Garden Sustainability Checklist for SGA’s GGP members.